Railway switch operating apparatus



Nov. 10, 1931. w. c. McwHlRTr-:R

RAILWAY SWITCH OPERATING APPARATUS Filed March 18, 1930 Patented Nov. 1:0, 1-931 UNITED STATES PATENT OFFICE WILLIAM o. Itrcwnnvrnn,A or wILxNsBUnG, PENNSYLVANIA, AssIGNoR To THE UNIoN SWITCH SIGNAL` COMPANY, 40]? PENNSYLVANIA RAILWAY SWITCH OPERATING APPARATUS i Application led March 18, 1930. Serial No. 436,718.

. the switch from one extreme position tothe other by a switch operating device, and which will permit the switch points to be freely movedaway from either extreme position by a trailing vehicle, but which will retard the returnof the switch points to their initial positions after such vehicle has trailed through the switch.

I will describe one form of apparatus embodying my invention, and will then point a: out the novel features thereof in claims.

In the accompanying drawings, Fig. lis a top plan view, partly cross-sectioned, showing one form of apparatus embodying my invention. Fig. 2 is an enlarged sectional View on the line .l1-Hof Fig. 1. Fig. 3 is an enlarged sectional view on the line III-III of Fig. 1. Fig. 4 is an enlarged fragmental sectional view on the line IV-IV of Fig. 3. Fig. 5 is an enlarged sectional view on the line r v-v of Fig. 1.

Similar reference characters refer to similar parts in each of the several views.

Referring rst to Fig. 1, the reference character A designates a railway switch, and the reference character `B designates a device for operating it. The switch A comprises, as usual, two iixed rails 1 and 1, and two movable switch points 2 and 2a, the switchpoints being connectedtogether near their tips by a front rod 3.

The operating device B, as here` shown, comprises a switch stand 14 having its base 15 spiked or otherwise secured-to the ties adjacent the switch A. A vertical shaftV 16,

journaled in the switch stand 14, ca rriesa` crank E21 and a gear segment 17. lThe gear segment 17 meshes with a'bevel pinion 18 keyed to a pinion shaft 19. The pinion shaft 19 extendsthrough the side of the switch stand 14 and has attached toits outer end the usual weighted switch-throwing lever 20.

The crank 21 of the switch' stand 14 is operatively connected with the front rod 3 of the switch A by means of a link 13? and a spring connecting rod C. The'spring connecting rod C may have any ,suitable form, but in the well known form here shown, this connecting rod comprises a cylindrical housing 10 having a lateral extension 10b attached to a bar 13 which is pivotally attached to the link 13a. The left-hand end 10a of the housing 10 has a smaller diameter than the body of the housing, while the right-handV end .is threaded to receive a cap 11 having an end 11a similar to the end 10a. Slidably mounted in the opening in the end 10a is a sleeve 8 provided with anl annular flange y8a located within the housing 10, and similarly mounted in the opening'r in the endv 11a is a sleeve 22 provided with an annular flange 22a'also located within the housing 10. A spring rod 7 extends through both sleeves with sufficient clearance to permit thev rod to slide freely in the sleeves, and this rod carries va compression spring y12 which engages the sleeves at i the annulary flanges andurges the sleeves toward the positions in which the annular flange 8a of the sleeve 8 engages the shoulder formed on the inside of the housing by the end 10a, and the annular iiange 22a of the sleeve 22 engages the shoulder formed on the swIssviiLE, PENNSYLVANIA, A CORPORATION oF inside of the cap 11 by the end 11a. Both i ends of the spring rod'are threaded and the left-hand end is provided with two nuts Q3, whilethe right-hand end of the rod is provided with a jam nut 6a and ascrew jaw 6. The screw jaw 6 is pivotallyattached to the front rod 3. i

The apparatus thus far desoribedis ywell known in the art and its operation' will be readily understoodfrom an inspection of the drawings. Y Y y Associated with the spring connecting rod C isa buiiing device D which, in the form here shown, comprises a casing 35 having a cylinder 35i extending therethrough, as best seen in Fig. 3. One end of the cylinder 35a is closed by a cylinder head 36 and the other end is"closed bya cylinder head 37. v A piston rod 39 extends into the cylinder 35a through a stuliing box 37 andthrougha suitable hole 37b in the cylinder head 37 and is attached', at its inner` end, to a reciprocable `piston 38 by'means of a castle nut 40. n The piston 88 is provided ywith an annular groove 38 and roo fst

with a plurality of holes 38.a which are arranged in a circle about the piston, and which communicate with the groove 38b for at times permitting the passage of fluid through the 1 piston as will be explained more fully hereinafter. The side of the groove 38b'adjacent the holes 38a is finished to form a valve seat, and constantly .urged againstthis valve seat by means of acoil spring 44, is'an annular valve 41 having an annular flange '41a' which nts within the adjacent end of the spring 44 to hold the valve in its proper position.

The cylinder wall is provided at its lefthand end with a leal; groove b which permits fluid to flow past the piston 33 'under certain conditions as will be made clear hereinafter.

Located in the casing 35 `above the cylinder 35a is a reservoir 43 which is constantly connected with the cylinder 35a on the righthand side of piston 38`tlirougl1a portf42. The reservoir 43 is also constantly connected with the cylinder 35a onthe left-hand side of piston 38, through a port 49 in the reservoir wall and a passage in the cylinder head 36. As here shown, the passage in the cylinder head 36 comprises two ports 48 and 49,11 regulating valve 47, which I will describe presently, v'being interposed between these ports to control theflow of fluid through the orts. The reservoir 43 and cylinder '35a are'botli intended to be filled with a suitable fluid such as oil, and in order to permitthe insertion of fluid into the reservoir'and the cylinder,'thereservoir wall is provided'with a hole 45 which is normally closed by a screw plug 45.

The regulating valve 47 may have any suitable form but,in the form here shown, this Valve comp-rises a cylindrical valve member 47C `(see Fig. 4) fitting in a hole 55 in the cylinder head`36, andattached to a valve stem 47d. The valve member 47C is provided with a plurality of restricted orifices 47a of di'derent sizes which extendrthro'ugh its side in radial spaced relation and 'any one'of which maybe brought into registration with the port 48 by turning the valve member 47C. To facilitate turning the valve member 47, the valve stem 47d is provided,`a't Vitsupper end, with a saw lierf 47h adaptedto receiveV the end of a screw driver. The valve is'held in place in the hole in 'the cylinder head 36 by 'a gland 52 which surrounds'the valve Vstem 47d, and which is 'fastened tothe cylinder head 36 by means of two stud bolts 51` each of which passes through a h0le'152" in a lug 52a integral with the gland 52, and each of which is screwed vinto a suitable threaded hole in the cylinder head 36. Suitable packing 54 is inserted between the gland 52 and the shoulder formed at the top of the lvalve member 47 c, and between the bottom of the gland and the cylinder head 36 to;prevent fluid from leaking past the valve.

post 24as best seen inFig. 2. Pivoted at one end on thisfpostare two oppositely disposed links 26 and 27. The link 26 comprisestwo straps 26a and 26b secured together by rivets A26d but'spaced-from each other by spacing members 26c and, in a similar manner, the link 27 comprises two straps 27" and 27" secured together by rivets 27d but spaced from each other by spacing members 27C. The free end of the strap 26ais offset to form a jaw, and'pivoted intermediate its ends on a pin 29 whiclrpasses through this jaw isa fulcrum bar 30. Oneend of fulcrum bar 30 is pivotally connected with the cylinder head 36 of bufling device D by means of a pin 56 which extendsthrough the bar and throughV two lugs 36a integral with the cylinder head 36. The other end of the bar v30 is pivotally connected with the sleeve 8 of the connecting rod C by means' of two trunnions 9a and 9" which are formed on'a nut 9 screwed onto the end of the sleeve '8 ofthe resilient connecting rod C. These trunnions extend through aligned holes inthe'bar 30, and in a member 30 riveted to thjebarl30,`as best seen in Fig. 5. The free end of the strap2a is also offset to form a jaw, andpivoted intermediate its ends on a pin'3'1'which passes through this jaw is a ful'crum bar 32. rIhe fulcrum bar 32 is similar to the 'ful'crum bar 30, and is pivot-ally attached at oneend to the piston rod 39 of the bufiing device D by means of a screwaw 50. r:["he other end of the fulcrum bar 32 is pivotally `attached to the sleeve 22 of the spring connecting rodC by means oftwo trunnions which pass through aligned holes in the bar 32 and in a member 32a riveted to the bar 32. These trunnions are formed on a nut which is not shown inthe drawings but which is similar tothe nut 9 screwed ontothe sleeve 8. In order, to assist in supporting the weight'of the bulfing device D, a plate 34 is inserted between lthe bai` 30 and the tie, and a similar plate 33 is inserted between the bar`32 and the tie. These plates may be fastened to'the tie in any convenient manner.

The operation of the apparatus as a whole is as follows: lhen switch A occupies the extreme position in which it is shown in the drawings, the parts of buffing device D occupyl the positions in which they are illustrated kin 3,-that is to say, ypiston 38 is Vat the.left.hand end of ycylinder 35a, and valve 4'1Yisv held closed by spring 44. If, now, it is desiredto reverseswitch A, switch throwing .lever 20 is rotated through an angle of 180 'from the `position in which it is illustratedin the drawings, thereby rotating gear segment/17 andcrank 21 in a counter-clock wise direction and, hence, moving bar 13 of connecting rod C toward the right. The motion of the bar 13 `toward the right is transmitted to the switch points 2 and 2 through the end 1()a of the housing 10, sleeve 8, spring 12, sleeve 22, screw jaw 6 and front rod'3, and the switch pointsare thereforeinoved from the extreme positions in which they are illustrated in the drawings to their other eX- treme positions. During this movement of the parts, there is substantially no relative movement between the sleeves 8 and 22 'of the spring connecting rod C,`and the fulcrum bars30 and 32 are therefore both rotated in a counterclockwise direction together, vas will be apparent from an inspection of the drawings. As a result, the bufng device D is moved to the left as a unit an amount depending upon the proportioning of the parts, and there is no relative movement between the piston 38 and thecasing 35. It will be apparent, therefore, that` under these conditions, the bufiing device D offers no opposifrom one extreme position to the other.

If after the switch has been reversed, it isy desired to restore the switch to the position in which it is illustrated in the drawings, the switch throwing lever 20 "is returned to the position shown. Under these conditions, the operation of the apparatus is just the reverse of that described hereinbefore, as will be apparent from an inspection of the drawings, so that the parts are all restored to the positions in which they are illustrated in Fig. 1. It should be pointed out that under these conditions also, there is no relative movement between piston 38 of buffing device lD and casing 35, and that bufiing device D does not oppose the movement of the switch points.

If a vehicle trails through the switch when the switch occupies the extreme position in which it is illustrated in the drawings, the vehicle wheels engage the switch point 2 and move the switch points toward the right. Spring rod 7 and sleeve 8 are therefore moved toward the right a like amount, but housing 10 and sleeve 22 are held stationary by switch operating device B. Spring 12 therefore becomes compressed, and exerts a force on the switch points which tends to restore the switch points to their initial positions. When sleeve 8 is moved toward the right, fulcrum bar 30 is rotated in a counterclockwise direction about pivot pin 29, so that casing 35 of bufiing device D is moved toward the left, but piston 38 of buffing device D is held fixed under these conditions, because sleeve 22 holds fulcrum bar 32 in the position shown. As a result, the fluid in cylinder 35a on the right: hand side of piston 38 flows through leak groove 35b into cylinder 35a on the lefthand side lof piston 38 until casing`35 has moved to the left far enough sothat the right-hand end of leak g`rofi` vey35b is pastthe right-hand' side of piston 38, whereupon the pressure of the fluid in'cylinder 35EL on the right-hand side of piston 38 opens valve 41 and permits fluid to flow throughy the holes 38a in piston 38 into cylinder 35EL on the left-hand side of piston 38. The pressure exerted on valve 41 by spring 44 is comparatively small, so that very little pressure is required to open valve 41. It will be apparent, therefore, that very little force is required to move casing`35 of buffing device D toward the left under these conditions, so that the resis ance oif'eredby bufling device D from their initial positions is very slight. As

soon as spring 12 starts to return the switch i points to their initial positions, however, sleeve 8 is moved toward the left, and casing 35 is moved toward the right. Piston 38 is still held fixed, and spring 44 now closes valve 4l, so that fluid can not pass this valve.V Furthermore, since the right-hand end of leak groove35b is now to the left of the right-hand side of piston 38, fluid is also prevented from flowing past the piston through leak groove 35b and, yas a result, the rate at which the switch points can return to their initial positions limited tothe rate at which the fluid in cylinder 35a on the lefthand side of piston 38 can flow through regulating valve 47, until casing` 35 has moved toward the right far enough to permit fluid to fiow through leak groove 35b past the piston 38. rlhe -rate'at which fluid can flow through regulating valve 47 may be varied by turning the valve 47 to change the orifice 4,7a which is in registration with port 48, and this rate will usually be adjusted to such a value that the switch points will not return to their initial positions until a time interval has elapsed which is longer than the time interval required for adjacent trucks of a vehicle to pass the switch points when the vehicle is moving at its usual speed.

W hen the switch points have returned toward their original positions far enough to cause the leak groove 35b in cylinder 35 to be uncovered by the piston 38, the opposition offered by the device D tothe return movement of the switch points is materially decreased and it is therefore apparent thatwith my invention the first part 'of the return stroke of the points is materially retarded,

while the latter portion of this return stroker tiallyv no opposition is offered by the buliing device-to normal manual operation of the switch or to movement ofl the-switch points away from either extreme position by a trailing railway vehicle, but the return move-l ment of the points after a trailing move is retarded to a degree which'ca-n be accurately controlled by valve 47.

Une advantage of apparatus embodying my invention is that due to 1 he method of supporting the buliing device D no heavy load is applied to the spring connecting rod C.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modications may be made therein within the scope of the appended claims without departing from the spirit and scope oi my invention.

Having thus described my invention, what I claim is:

l. The combination.,` with a railway switch comprising a switch point movable between two extreme positions and an operating device connected with said switch point through resilient means for moving said switch point to either of said extreme positions, of a cylinder containing a reciprocable piston, link work for connecting said cylinder and said piston with said resilient means in such manner as to permit relative movement of said piston and said cylinder when said switch point is trailed through by a vehicle but not when said switch point is operated by said device, andmeans for permitting free relative movement of said piston and said cylinder in one direction and for retarding relative movement of said piston and said cylinder in the opposite direction.

Q. The combination, with a railway switch comprising a switch po-int movable between two extreme positions and an operating device connected with said switch point through resilient means Jfor moving said switch point to either of said eXtreme po-sitions, of'V a bufling device comprising a casing provided with a cylinder containing fluid, a reciprocable piston in said cylinder, a piston rod extending into said cylinderand attached to said piston, a valve in said piston arranged to permit the flow offluid through said piston in one direction, and av variable by-pass around said piston; and means for connecting said casing and said piston rod with said resilient means in such manner as to permit relative movement of said piston and said cylinder when said switch point is displaced from an extreme position by a vehicle but not when said switch point isoperated by said device.

3. The combination, with a railway switch comprising a2 switch point movable between two extreme positions and an operating device connected i Yith said switch point through resilient means for moving said switch point igssas to either of said extreme positions, of a buffmgfdevice comprising a casing provided with a cylinder containingfluid, a reciprocablel piston in said cylindeiga piston rod extending into said cylinder and attached to said piston, means for permitting iuid to iiow past saidpiston for a portion of its stroke, a valve in said piston arranged to permit the flow ofrfiuidthrough said piston in one direction, and a variable by-pass around said piston; and means for connecting said casing and said piston rod with said resilient means in such manner as tov permit relative movement of said piston and said cylinder when said switch. point is displaced from an eXtreme position by a vehicle.

4. j The combination, with a railway switch comprising a switch point movable between two extremeV positions and an operating device connected with said switch point through resilient means for moving said switch point to either of said extreme positions, of a buffing device comprising a casing provided with a cylinder containing fluid, a reciprocable piston in said cylinder, a piston rod extending into said cylinder and attached to said piston, means at one end of said cylinder for permitting fluid to flow past said piston during aV portion of its stroke, a valve in said piston arranged to permit the flow of iiuid through said pistonin one direction, and a variable by-pass around said piston; and means for connectingfsaid casing and said piston rod with said resilient means to cause relative movement of said piston and said cylinder when said switch point is displaced from an extreme position by a vehicle but not when said switch point is operated by said device.

5. The combination, with a railway switch comprising a switch point movable between two extreme positions and an operating device connected with said switch point through resilient means for moving said switch point to either of said extreme positions, of a buffing device comprising a casing provided with a cylinder containing a fluid, a reciprocable piston in said cylinder, a piston rod extending into said cylinder and attached to said piston for reciprocating said piston, said cylinder being provided at one end with a leak groove to permit fluid to flow around said piston for a portion of its stroke, a valve in said piston arranged to permit the flow'of fluid through said piston in one direction, and a variable by-pass around said piston; and means for connect-ing said casing and said piston rod with said resilient means to cause relative movement of said piston and said cylinder when said switch point is displaced from an extreme position by a ve- -hicle but not when said switch point is operated by said device. v

6. .In combination, a railway switch movlll? able Abetween two eXtreme positions, a switch .4.50

spring and two movable sleeves so 'arranged that it said switch is moved to either extreme position by said switch operating device said sleeves will remain in fixed relation with respect to each other but that-if said `switch is trailed through in an extreme position said sleeves will move relatively to each other and stress said spring to permit movement of said switch, two i'ulcrum hars each having; one end pivotally connected with one of'said sleeves, a fixed post7 two links each having one end pivoted on said post and having; the other end pivotally connected with one of said tulcrum bars intermediate its ends, and a buiing device pivotally connected between the free ends of' said fulcrum bar and arranfed to permit tree relative movement of' said sleeves in one direction but to retard relative movement of' said sleeves in the opposite direction. 1

A'7. In combination, arailway Vswitch mov* able between two extreme positions, ya switch operating device, a connecting rod for connecting said switch operating device with said switch, said connecting rod including a spring and'two movable sleeves so arranged that if said switch is moved to either extreme position b v said switch operating device said sleeves will remain in fixed relaton with respectto each other but that if said switch is trailed through in an extreme position" said sleeves will move relatively to each other and stress said spring to permitmovement ot said switch`v two fulcrum bars each having' one end pivotally connected with Vone of said sleeves a fixed post, two links `each having one end lpivoted on said post and having the other end pivotally connected with one of said ulcrum bars intermediate its ends, and a boiling device pivotallv connected between the free ends oi said tulcrumv bars and arranged tol permit` free *relative movement of said sleeves due to movement of the switch points but to retard movement of said sleeves due to said spring.

8. In combination; a railway switch movable between two extreme positions, a switch operating device*` a connectingr rod for conmeetingsaidy switch operating deviceV with said switch, said connecting rod including a springT and two movable sleeves so arranged that if said switch is moved to either eXtreme position bv said switch operating; device said sleeves will remain in fixed relation with respect to each other but that if said switch is trailed through in an extreme position said sleeves will move relativela.7 to each other and stress said spring' to permit movement o said switch, two fulcrum bars each havin( one end pivotallv connected with one of sain.

sleeves` a fixed'post. two links each havingr one end pivoted on said post and having the vother endpivotally connected with one ofsaid fulcrum bars intermediate its ends a buiiing device comprising a casing provided with a cylinder containing a fluid, a reciprocable piston in said cylnder, a piston rod extending i into said cylinder and attached to said piston for reciprocating,l said piston, a valve insald piston arranged to permit the low of fluid' through said piston in one direction, anda 4variable by-pass around said piston; means for pivotally connecting said casing to the free end ot' lone of said i'ulcrumv bars, and means for pivotally connecting said piston lrod withthefree end of the otherv said fulsaid switchv` two fulcrum bars each having one end pivotally connected with one ot said sleeves` fixedr post, two links each having one end pivoted on said post and having the other `end pivotallyv connected with one of said ulcrum bars intermediate its ends: a builingr device'comprising a casing' provided with a cylinder containing a fluid, a ref ciprocable piston in said cylinden a piston rod extending into said cylinder and attached to said piston for reciprocating said-piston, a valve in said piston arranged toA permit the flow of luid ythrough said piston in one direction. and a bv-pass around said piston in cludino avalve forregulating the flow of fluid through saidbv-pass, means for pivot-Y allyr connecting saidl casing to the free end of one of said fulcrum bars, and means tor pivotallv connecting said piston rod with the y one of said sleeves will be held'fiXed and the.

otherwill move 'towardsaid one sleeve and compress said springV to permit movement of the switchfaway from vsaid one extreme position and that if said,V switch is trailed through in the other extreme position said other sleeve willfbe held iXed and said one iso sleeve will'move toward'fsaid: other'sleeve and compress said spring toV permit movement of the switch awa7 fromsaid other'extreme position, two fulcrum bars each having one end pivotally connected with one of said sleeves, a fixed post, two links each havingone end pivoted on said post and having the other end pivotally connected with one of said fulcrum bars intermediate its ends, a buffing device comprising al casing provided with a cylinder containing a fluid, a reciprocable piston in said cylinder, a piston rod extending into said cylinder and-attached to 'said piston for reciprocating said piston, a valve in said piston arranged to permit the fiow of Huid through said pistonin one direction, and a by=pass around said piston including one or more restricted orifices, means for pivotally connecting said casing to the free end of oneof said fulcrum bars, and means for pivotallvconnecting said piston rod with the free end of the other said fulcrum bar.

l1.A Incombination, a railway switchvhavinfr switch points `movablef between two eX- tremepositions, a switch operating device; a

springV connecting rod comprising a 'housing connected with-said switch operating device and4 provided Ywith'aligned openings, two sleeves, one arranged to slide freely ineach'of said openings and each having an integral flange located on thef-insideof saidhousing and adapted to at times engage the'finsideof said housing adjacent said openings, aspring in said Vhousing arranged to urge said sleeves to thepositions-in which ysaid .flanges engage said housing` anda spring rodv extending freely through said spring and said sleeves andconn'ected kat onev end withthe switch pointsand provided with meansY for at times engaging oneY or the other of 'said sleeves at its outer end; twofulcruin bars each havingone end -pivotallyy connected with one of said sleeves'Y a fixed post, two links Veach having one-end pivoted on said postfandhaving the other end pivotallv con'nectedfwithY one of said fulcrumbars intermediate its ends, and a buffing devicepivotally connected between the freeends of said'fulcruna bars:

l2. Incombi-nation, a railway switch having switch pointsuiovable between twofeX- treme positions, a switch Voperating device; iaspring connecting rod comprising a housing connected with said switch operating device and provided with aligned openings, two sleeves, one' arranged to slide freely in 'each of said openings and each having an' integral flange located'on the'-Y inside of said housing and' adapted to at times engage the inside of said housing 'adj acent said openings, a spring in said housing arranged to urge said sleeves toward the'positions in whichsa'id flanges engagefsaid housing, and a spring` rod extending freely'through' said spring and said sleeves and connected at one end with thefswitch pointsand provided with means for at times engaging `one'or theother of'saidsleeves at its outer end; two fulcrum bars eachV having one end .pivotally connected with one of said sleeves, aiixed post, two links each having. one end pivoted on said post and having theotherend pivotally connected with one of said fulcrum bars intermediate its ends,^a bufiing device comprising a casing provided with acylinderk containing a fluid, a reciprocable piston in said cylinder, a piston rod extending into said cylinder and attached to said piston for reciprocating said piston, a valvein said piston arranged to permit the flow of fluid through said piston in one direction,- and a by-pass around said piston includinga restricted orifice; means for pivotallyconnecting. said casing to the free end of one of said fulcrum bars, and means for pivotally connecting said piston rod with the free end ofithe other said fulcrum bar.

13. In combination, a railway switch mov` ablebetween .two extreme positions, a switch operating device, a spring connecting rodfor connectingsaid switch operating device with saidswitch, said connecting rod including'a spring and two-movable sleeves so arranged that if said switch is moved to eitherextrelne position by' said operating device said sleeves willamove together but that if said switch is trailed through in one eXtreme position one ofsaid'sleeves will he heldfixed and the other willfmove toward said one sleeve and compresssaidspringtoV permit movement of the switch away from said one eXtreme position and thatif' said switchis trailed tie-rough in the other extreme 'position said other sleeve will -beheld fixed and said one sleeve will move toward said other sleeve and compress said spring to permit movement of the switch awayfrom said other extreme position, two fulcrum barseachl having one end pivotally connected with one of said sleeves, afixed post, two links eachhaving one end pivoted onrsaidpost? and having the other end pivotally connected with one of said fulcrum bars intermediate its ends, a bufiing device comprisingy a casing provided with a cylinder containing` a fluid, a reciprocable. piston in said cylinder, a piston rod extending into said cylinder andattached to said piston vfor reciprocating said'piston, said cylinder being provided at one end with a leak groove to permit fluid to flow around said piston for a portionvof its'stroke, a valve in said piston arranged to permit the'flow of fluid through safid piston in one direction, and a by-pass around said piston including a restricted orifice,V means for pivotally connecting said casing to the/free end of one of said fulcrum bars, and means for pivotally connecting said piston rod with the tree end of the other said fulcrum bar. t l

In testimony whereof I affix my signature.

VVLLIAMr C. MoWI-HRTER. 

